Camshaft adjuster

ABSTRACT

A camshaft adjustment device for an internal combustion engine, having a stator ( 1 ) that can be driven by a crankshaft of the internal combustion engine, having a rotor ( 3 ) that can be connected rotationally conjointly to the camshaft, having working chambers which are arranged between the stator ( 1 ) and the rotor ( 3 ) and which are divided into first and second pressure chambers (A, B) by vanes ( 18 ) assigned to the rotor ( 3 ), wherein, in the rotor ( 3 ) there are provided first pressure medium ducts ( 5 ) which issue into the first pressure chambers (A) and second pressure medium ducts ( 6 ) which issue into the second pressure chambers (B), wherein the rotor ( 3 ) has an inner ring ( 15 ) and an outer ring ( 14 ) which are connected to one another by means of a disk-shaped web ( 9 ), and the first pressure medium ducts ( 5 ) are arranged on one side of the web ( 9 ) and the second pressure medium ducts ( 6 ) are arranged on the other side of the web ( 9 ), and the first and second pressure medium ducts ( 5,6 ) are formed by pressure medium guiding sleeves.

The present invention relates to a camshaft adjuster.

BACKGROUND

Camshaft adjusters are used in modern internal combustion engines foroptimizing the consumption and performance values and are used to changethe opening and closing points in time of the gas exchange valves. Forthis purpose, the camshaft adjuster includes a stator which is drivableby the crankshaft and a rotor which is rotatably fixedly connectable tothe camshaft. Working chambers, to which a pressure medium may beapplied and which are divided into oppositely acting pressure chambersby vanes assigned to the rotor, are provided between the rotor and thestator. During the operation of the internal combustion engine, bothpressure chambers are permanently filled with pressure medium, so thatthe rotor and the stator are connected to each other relatively rigidly.The control times of the gas exchange valves are then changed, in thatthe pressure is increased in one of the pressure chambers, while thepressure is reduced in the other pressure chamber. For this purpose, thepressure medium must be supplied to the one pressure chamber and removedfrom the other pressure chamber. To avoid causing the system to vibrate,the inflow of the pressure medium must, in principle, be controlled bythe outflow of the pressure medium.

Pressure medium channels must furthermore be provided in the rotor,which empty from the hub of the rotor into the pressure chambers of therotor. The pressure medium channels are fluidically connected in twogroups each to two annular spaces, which are provided radiallyinternally on the rotor, and are separated from each other pressuremedium-tight and to which pressure medium may be applied with the aid ofa central valve. For this purpose, the central valve includes aspring-loaded valve body, which is movably situated in a control sleeveand which is movable against the spring force with the aid of anactuator in the control sleeve. A complex geometry of control edges isprovided in the control sleeve, with the aid of which the pressuremedium flowing through the valve body flows out into the annular spaces,the pressure medium channels and finally into the pressure chambers. Forthis purpose, the valve body has a hollow design and closes and openscertain flow paths using different control edges as a function of itsposition, so that the pressure medium flows into the first pressurechambers in one position of the valve body and into the second pressurechambers in another position, while it flows out of the respective otherpressure chambers into a tank.

The regulating speed of the camshaft adjuster as well as the vibrationbehavior of the moving parts is greatly dependent on the own weight ofthe parts, the rotor, in particular, as a particularly large mass,significantly influencing the control behavior. For reasons of use invehicle manufacturing, it is, in principle, also desirable to usecomponents having a low own weight. For this reason, recesses arealready provided in the rotor to the extent permitted by the course ofthe pressure medium channels.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a camshaft adjusterhaving a preferably low own weight and a preferably simply structuraldesign.

The present invention achieves the object with the aid of a camshaftadjuster;

The present invention provides that the rotor has an inner ring and anouter ring, which are connected to each other by a disk-shaped web, andthe first pressure medium channels are situated on one side of the weband the second pressure medium channels are situated on the other sideof the web.

The advantage of the provided camshaft adjuster is to be seen in thatthe rotor has a significantly lower weight, due to the provided designhaving the inner ring, the outer ring and the web connecting the innerring and the outer ring. The pressure medium is supplied separately tothe first and second pressure chambers and then through the web, so thatthe web has the function of separating the pressure medium flows inaddition to connecting the outer ring and the inner ring. Furthermore, aprevolume is created for accommodating pressure medium due to thecavities created laterally to the webs, which may be introduced backinto the pressure chambers, for example by utilizing the camshaftalternating torques.

It is furthermore provided that the first and second pressure mediumchannels are formed by pressure medium guiding sleeves. The pressuremedium guiding sleeves are much lighter than the solid materialpreviously used, including the pressure medium channels situatedtherein. Moreover, due to the provided arrangement of the pressuremedium guiding sleeves on different sides of the web, a simpler basicstructure is achieved, which has a very high rigidity of the rotor,since the web may be preferably situated in the middle between the innerring and the outer ring. A sufficient clearance for situating thepressure medium guiding sleeves thus remains on both sides of the web,so that they may be situated laterally offset from each other, andannular spaces which are spaced axially apart and are separated fromeach other pressure-medium-tight may be connected to the pressure mediumsystem. The pressure medium guiding sleeves are furthermore separatedfrom each other by the web, due to the provided arrangement, so that ahydraulic short circuit between pressure chambers A and B may beprevented in the event of possible leakage of the connecting points ofthe pressure medium guiding sleeves into the openings of the inner ringand the outer ring.

It is furthermore provided that the inner ring and the outer ring aresituated concentrically to each other, so that a preferably uniformdistribution of mass results with preferably little imbalance. Since therotor rotates together with the camshaft at a relatively high rotationalspeed, an imbalance is particularly disadvantageous for the operatinglife of the camshaft adjuster itself and the operating life of theentire internal combustion engine.

According to another preferred specific embodiment of the presentinvention, it is provided that the first pressure medium guiding sleevesare situated in a first plane and the second pressure medium guidingsleeves are situated in a second plane. Due to the provided arrangementof the pressure medium guiding sleeves, they may be connected to thepressure medium system with the aid of preferably narrow, annular spaceswhich are separated from each other pressure medium-tight, a masscompensation being furthermore particularly easy to implement, due tothe provided arrangement.

The structure and the mass compensation may be further simplified inthat the first plane is situated in parallel to the second plane, and/orthe first and second pressure medium guiding sleeves are situatedequidistantly from each other in the planes in the circumferentialdirection.

It is furthermore provided that the first and second pressure mediumguiding sleeves are formed by straight tube sections. Due to theprovided design of the pressure medium guiding sleeves, the massdistribution may be further simplified. In addition, cost-effectiveseries-production parts may be used.

It is furthermore provided that the first and second pressure mediumguiding sleeves have identical masses, whereby the mass compensation maybe further simplified.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is explained in greater detail below on the basisof one exemplary embodiment. The following are shown in detail in thefigures:

FIG. 1 shows the stator and rotor of a camshaft adjuster according tothe present invention;

FIG. 2 shows the rotor in sectional direction A-A; and

FIG. 3 shows an oblique view of the rotor.

DETAILED DESCRIPTION

Apparent in FIG. 1 are a stator 1 and a rotor 3 of a camshaft adjusteraccording to the present invention, which has a basic structure knownfrom the related art, including stator 1, which is drivable by acrankshaft, and rotor 3, which is rotatably fixedly connected to acamshaft, which is not illustrated. Stator 1 includes a toothing 2 onits outside, with which a drive chain engages, which transmits therotary motion of the crankshaft in rotation direction “D.” Stator 1 isprovided with inwardly directed projections 4, which divide the cavitybetween stator 1 and rotor 3 into working chambers. The working chambersare further divided into pressure chambers A and B by vanes 18 situatedon rotor 3, vanes 18 being supported on stator 1 with their radialoutsides with the aid of seals 8. Pressure medium channels 5 and 6 areprovided in rotor 3, to which pressure medium is applied by an oil pumpwith the aid of a central valve, which is not illustrated, or whichremove the pressure medium to a tank with the aid of the central valve.Pressure medium channels 5 and 6 empty into pressure chambers A and B,the pressure medium being removed into a tank from pressure chamber A orB to which pressure medium is not applied when pressure is applied toone of pressure chambers A or B by the oil pump.

Pressure medium channels 5 and 6 are each designed as pressure mediumguiding sleeves in the form of short, straight tube pieces of equallength and mass. First pressure medium channels 5 empty into firstpressure chambers A, and second pressure medium channels 6 empty intosecond pressure chambers B. In the illustrated exemplary embodiment,rotor 3 includes four vanes 18 and correspondingly four first pressurechambers A and four second pressure chambers B, which are separated fromeach other by vanes 18. First pressure chambers A and second pressurechambers B differ from each other in that they are situated in groups onthe same side of vanes 18, so that rotor 3 is rotated clockwise withrespect to stator 1 when pressure is applied, for example to firstpressure chambers A.

Rotor 3 is formed from an outer ring 14 and an inner ring 15, which areconnected in the middle with the aid of a web 9 in the form of a disk.The disk has a constant width in the radial direction, so that innerring 15 and outer ring 14 are situated concentrically with respect toeach other, as is also apparent in FIG. 3. Radially outwardly directedvanes 18, which divide the working chambers into pressure chambers A andB, are provided on outer ring 14. The disk connects outer ring 14 andinner ring 15 in the middle, so that clearances 7 are present laterallyto the disk, as is apparent in FIG. 2. First openings 11 and 13 arefurthermore provided in inner ring 15 and in outer ring 14,respectively, laterally to the disk on one side, and second openings 10and 12 are provided on the other side, into which the pressure mediumguiding sleeves are inserted. First openings 13 in outer ring 14 emptyinto first pressure chambers A, and second openings 12 in outer ring 14empty into second pressure chambers B in an edge section of outer ring14 adjacent to vanes 18. First openings 11 and 10 in inner ring 15 emptyinto annular spaces 17 and 16 provided radially on the inside of innerring 15, to which pressure medium may be applied with the aid of thecentral valve, which is not illustrated.

The pressure medium guiding sleeves may preferably be made of steel.Alternatively, pressure medium guiding sleeves made of aluminum orplastic could also be used. The pressure medium guiding sleeves maypreferably have a round cross section, but alternatively also an oval,polygonal or even square cross section. The fastening of the pressuremedium guiding sleeves on inner ring 15 and on outer ring 14 may takeplace, e.g., with the aid of a thread, an integral fit, a form-lockedfit or a force fit. The pressure medium guiding sleeves preferably allhave the same mass and identical dimensions, so that rotor 3 has apreferably minor imbalance, due to an identical arrangement of thepressure medium guiding sleeves in the radial direction and anequidistant arrangement in the circumferential direction.

It is furthermore important that first pressure medium channels 5 andsecond pressure medium channels 6 formed by the pressure medium guidingsleeves are situated in groups on different sides of web 9, so that ahydraulic short circuit between pressure chambers A and B may beprevented by web 9, even in the event of a possible leak of theconnecting points of the pressure medium guiding sleeves in openings 10,11, 12, 13 of inner ring 15 and/or outer ring 14. Surprisingly, it hasfurthermore turned out that, due to the laterally offset arrangement offirst and second pressure medium channels 5 and 6, it may be ensuredthat a small remnant of pressure medium always remains in pressurechambers A and B and in the prevolume between outer ring 14 and innerring 15 or in the pressure medium guiding sleeves, even in the “advance”and “retard” stop positions, so that a small amount of pressure mediumis present in the camshaft adjuster even during the cold start phase,which at least reduces uncontrolled movements of rotor 3 with respect tostator 1.

LIST OF REFERENCE NUMERALS

-   1 Stator-   2 Toothing-   3 Rotor-   4 Projections-   5 First pressure medium channels-   6 Second pressure medium channels-   7 Clearances-   8 Seals-   9 Web-   10 First opening-   11 First opening-   12 Second opening-   13 Second opening-   14 Outer ring-   15 Inner ring-   16 Annular space-   17 Annular space-   18 Vanes-   A, B Pressure chambers-   D Rotation direction

1-8. (canceled)
 9. A camshaft adjuster comprising: a stator drivable bya crankshaft; a rotor rotatably fixedly connectable to the camshaft;working chambers situated between the stator and the rotor, the workingchambers divided into first and second pressure chambers by vanesassigned to the rotor; first pressure medium channels being provided inthe rotor, the first pressure medium channels emptying into the firstpressure chambers, and second pressure medium channels emptying into thesecond pressure chambers; the rotor including an inner ring and an outerring connected to each other by a disk-shaped web; and the firstpressure medium channels being situated on one side of the web, and thesecond pressure medium channels being situated on an other side of theweb.
 10. The camshaft adjuster as recited in claim 9 wherein the firstand second pressure medium channels are formed by pressure mediumguiding sleeves.
 11. The camshaft adjuster as recited in claim 9 whereinthe inner ring and the outer ring are situated concentrically withrespect to each other.
 12. The camshaft adjuster as recited in claim 10wherein first pressure medium guiding sleeves of the pressure mediumguiding sleeves are situated in a first plane, and second pressuremedium guiding sleeves of the pressure medium guiding sleeves aresituated in a second plane.
 13. The camshaft adjuster as recited inclaim 12 wherein the first plane is situated in parallel to the secondplane.
 14. The camshaft adjuster as recited in claim 12 wherein thefirst and second pressure medium guiding sleeves are situatedequidistantly from each other in the first and second planes in thecircumferential direction.
 15. The camshaft adjuster as recited in claim10 wherein the pressure medium guiding sleeves are formed by straighttube sections.
 16. The camshaft adjuster as recited in claim 10 whereinthe first and second pressure medium guiding sleeves have identicalmasses.